Process for treating fibrous materials



Oct. 13, 1931. c. LEYsT-KUcHl-:NMElsTl-:R 1,827,710

PROCESS FOR TREATING FIBHOUS MATERIALS Filed June 10, 1929 Patented oct. 13, 1931 CARL LEYST-XCHENMEISTER, F BERLIN-SCHLACHTENSEE, GERMANY PROCESS FOR TREATING FIBBOUS MATERIALS Application led June 10, 1929, Serial No. 369,869, and in vGermany .Tuly 28, 1928.

Up to the present all technical procedures for dissolving seinior full-cellulose stuffs by boiling from ligneous or strawlike raw materials have endeavoured to obtain the digesting results by the following methods:

1. By boiling a slowly rotating mass of raw material in a rotary cooker. 2. By using steam for boiling with the least possible quantity of water and under increased steam pressure.

3. By using steam for boiling stationary raw' material in a vertical 0r horizontal cooker.

- 4. By boiling e'ected by a sudden influx of steam into the stuff'.

These four procedures are considered scientifically and technically as closed and not improvable. With the exception of slight variations without changing the main prin- Y0 ciples. apparently no novel procedures are possible. I

It is therefore first of all necessary to explain that the errors and deficiencies of these four old procedures, are Very considerable,

"-5 so as to demonstrate comparatively the novel technical principles of hertofore unknown high-speed hydrodynamic disintegrating action and the frictional boiling process.

Using procedure 1, viz, boiling a rotating i0 mass of raw material no higher speed than 15 turns per minute as a maximum can be obtained. owing to the enormous Weight of the rotary iron cookers of 10 or more tons. Owing to this limited speed it is impossible to produce a noticeable'` movement of the raw 13 ticles of .stuff have no sufficient space inside the boiler. to .nove effectively .one upon the other. lVhat really happens is that the pressed up stuff slowly turns inside the cooker like an enormous cork inside the neck of a l bottle, without the pieces sliding over or rubbing against each other. Even if the cooker is only half filled. its speed of 12 to 15 turns p. m. is much too small to produce an effective l internal friction in the mass of stuff'. Vhen describing the high-speed process involving a hydrodynamic disintegrating motion the importance of a high-speed of 200 to 1200 turns increase of a brown-black colour of the stuff,

which becomes darker the longer the steam pressure acts upon the same. But owing to the fact that any corbonization only takes place under superheating, every partial carbonization signifies aproduction of semi-oxycellulose steps. Every fibre, consisting by nature of different steps of growth, changes over, when beingsuper-heated, in the same step of fibre variation into Oxy-cellulose or semi-oxy-cellulose, this being a preliminary grade of Oxy-cellulose. For the reason that therefore the exterior layers of the boiling stuff are principally exposed to being superheated, the largest quantity of Oxy-cellulose is produced in these layers, which, when exposed to the first washing process, is dissolved, causing a certain loss in output, while the semi-oXy-cellulose resisting the first washing, is dissolved. during the further procedures in the crushing'mills and finishers, there- ,b v further increasing the losses in output.

This is, for instance, the reason why cellulose which has been boiled under too high a pressure and then changed to viscose, and after squirting the viscose filament when entering the sulphuric acid bath, suffers excessive rupture of the filament through the dissolution of semi-oxycellulose. This is why up till now only the Swedes are able to produce wood cellulose for artificial silk viscose at low pressure and with careful bleaching. Also the cotton filament which is comparatively much tougher thanthe cellulose thread, loses considerably in tensile strength under pressure. The investigator Mr. Albert Scheurer has proved (Theis Die Breitbleiche Berlin,

lpublished by Krayn, pages 140-142) that cot.-

` ton filament having a tensile strength of `55 'cellulose process, which is carried out in huge digestors having an acid-proof tiled lining,

has the following disadvantages. Each layer of boiling stuff' has a certain gravity effect which increases from laver to layer. In a L cooker 50 feet high and 6 feet in diameter the lower layerup toa height ofy 6 ft. receives a hydraulic pressure of 31 metrical tons,`in creasing to 36tons at the bottom, viz. to 21.5 lbs. per sq. in. This pressureon each layer effects a compression of the fibre particles and therefore a closing up against the resorption or inflow of the lye. This is the reason why the composition of the lye must be much stronger than would appear to be necessary, the strength generally used being 3% sul-v phurous acid and 1% milk of lime, whereas from consideration of the individual wood chips, it might theoretically be 30% weaker. But owing to the high pressure of the layers a proportional increase of the strength of the lye is necessary to overcome this pressure" so as to enter into `the interior of the boiling l stuff. I-Iereby too much Oxy-cellulose is again formed in the outer layers, diminishing the output. In straw-like stuffs the pressure on d each layer increases a sticking-together tendency, viz. an-increase of the adhesion. It is therefore practically impossible to boil straw or similar materials in a stationary boiler, so that this stuff is always cookedin turning boilers, whereby the disadvantages explained under heading No. 1 appear over again.

If in the old procedures steam has been'the main factor, it is still necessary to describe the disadvantages of a sudden influx of steam as defined under heading 4. All strawlike stuffs absorb up to 200% either in a raw or in a developed state, all timber more or less up to 100%. These absorption phenomena :are of great importance in boiling. When the lyecan continuously penetrate into the raw stuff, due to this absorption, the latter is more uniformly digested. j ust as much in the center of the mass as in the exterior.l layers.` A similar absorption process cannot, however, sufficiently take place, if the steam is being suddenly admitted. Many paper manufacturers complain of the fact that inside the cooker socalled boiling provinces are formed on a sudden influx of the steam, which signifies that parts in the centre of the boiling mass are formed, which clearly show a (distinctly worse boilin effect and which at the end of the process,- ave not been as thoroughly digested as in the exterior layers. This unfavourable phenomenon is caused by the following. In allstrawlike materials a contraction of the cell-canals (lumina) at the sides of the straw takes place due to a too rapid influx. I-Iot steam being admitted, the pectine crusts which surround the cell canals as protective covers harden at first, soften very slowly as soon as the lye becomes hotter and begins to penetrate. But after this the time of action`is very considerably reduced. Taking 5 hours as boiling time, the lye requires, also when steam is suddenly admitted, at first one hour for heating (temperature rise) and more than 1 hour for the osmotic penetration into the boilin mass. But in this case orle third of the boiling time, has been used unproductively and has therefore been wasted. Without seeingthebiological reasons many paper manufacturers help themselves by a preliminary heating of the cooking lye. In reality the thermo-dynamicaltransition in the temperature from degree to degree is wanting, which favours the penetration of the lye and which does not come into action in a suflicient manner with a steam influx at 302 degrees F. All straw-like material as well as timber require thermo-dynamical degrees of temperature rise of say 50-68-104f176-212230248266-284-302 degrees F. so as to absorb the lyes as favourably as possible, so that the absorption and swelling, interdepending upon each other in an equal degree may take place from step to step in the shortest possible time. While this absorptionof the lyeby degrees is handicapped by a sudden inux of steam, it takes place step by step when applying frictional heat developedby a high-speed number of turns of the lye-mixers. .It favoursnand heightens the infiux of water and lye exactly in thesame space of time into the boiling mass, as this latter permits according to its natural swelling and absorption, as will be explained later on. Y

These disadvantages of the four old procedures are almost entirely removed by the novel cooking, milling and digesting process using a high speed motion of the raw-stuff'V \four cornered-shaft b onwhich is fixeddis- A lers can bearranged on the bottom.

tances of 7G-180 mm. from sword to sword (in specially cases to 220 mm.) rotary steel swords or knives c with sharp edges are fas-v tened. On the inside of. the drum a are fastened a certain number of stationary steel swords or knives d withsharp edges, each stationary sword d standing midway between two of the sharpened swords c. In an upper c hamber enclosed by a sieve-basket g-L are two propellersj and f.

Thel downwardly bent propeller f holds the dancing stuff down I while the upwardly bent propeller f' draws the dirty water or assortable stuff toward the top past a sieve-basket g-h in the putouthole z'. Similarly two upwardly bent propel- If the stuffis ready milled or washed or i bleached, the outlet hole m is opened, where- `25 upon the two lowermost swords c sweep out the stuff" automatically. Vhen dirty stuff is to be washed, a considerable surplus of fresh water is running in at the inlet hole n and the rotation diminished to half-speed, where- 'upon automatically the dirty water is drawn out at the headsieves g-L.' The same headsieves serve yalso for the first preliminary assorting after insertion of suitable assorting-,sieves The first assortable stuff can be assorted within half an hour. If the stuff is to be bleached, the engine' is filled through the inlet hole at the top, the charging of the stuffI being followed by running in the chloride of lime liquor. During the bleaching the rotation'is` diminished and specially here is shown the importance of the exact lonf` swords for avoidance of dangerous stunests. After the first preliminary bleaching, the first thinner bleaching liquor may be drained, followed by washing,and

then finish bleaching but it is also possible to carry through a perfect bleaching of two hours in one stage of manufacture. After finishing the bleaching the engine automatically is washed. The washing water again is run in'at the'bottom at n and led out again at the top g-L. The bleached stuff Lcan-because the engine consists preferably of acidsure founding and for bleaching-purposes is equipped with wooden movers and with 'a shaft covered 'with wood-the neutralizing also can be expected. Therewith the washing water at g--L fiows off lighter, the propeller f1 on the top is formed a little upwards. In this way the propeller ,f of the upper propellers presses the stuff downwards; the upper propeller f1 the washing water or the swimming assortable stuff upwards, therewith the stepping-out by the sieve-baskets g-h is lightened. For

'lo'I The sharp rotary swords c are revolved at a speed which may run as high as 1500 turns per minute, whereby firstly the water is slung against the fixed sharpened countercurrent swords or knives d, fastened radially to the inside of the iron drum. Through the velocity of the revolving water thrown against the fixed swords or knives a sudden Y back-How comes into action, which, similar to water acting under a high head of pressure, acts upon the material contained in the water, helping to disintegrate the same.

At the same time an internal friction takes place between the water, the raw material and both together between the revolving and fixed swords c and (l, owing to the high speed of turns. This friction develops heat by degrees, reaching inside of an hour a temperature up to 212 degrees F. equal to the boiling point.

Owing to this fri ctional heat a hydrolytical dissolving effect results which combines with the primary disintegrating factor, the motion of the water, andthe action of the .sharpened edges of the knives. i

Through the combined action of these factors a semi-cellulose is developed from the rawl material introduced into the drum without an addition of chemicals or any external heat, semi-cellulose from which a large part of the lignone and' incrusting matter has been already dissolved. Upon adding alkaline matter, or acids or neutral salts full cellulose is developed, the time of milling being increased, the cellulose which may be bleached, attaining a high degreerof tensile stren th and other good qualities.` Thebleaching process mayv be carried out when the' workl 1s finished 1n the same Universal-machine.

All these factors and novel technical effects take place in oneand thesame Universal-machine, Leyst system, so that ac` cording to the old system the iron-cooker,

y the beating-engine besides the stuffchest, the

finisher, the refiner and bleaching finisher altogether six units of the old system becomeA A extraordinarily simplifying the entire plant.l

I now have to present some proofs and explanations which will demonstrate these, novel effects. First ofall many paper manuduring the boiling process.

integration in the presence of water. In

connection herewith it must be clear that Schwalbe means hereby the forma-tion of Oxy-cellulose resulting from a mechanical disintegration of cellulose stuffs in water, and ynot from raw stuffs. It is a well known scientific fact, and .experience shows, that cellulose stirred in water just the same if milled or stirred, is partially dissolved forming. slimes. Thisknowledge is standard for cellulose hydration, but it is a novel factin connectionwith the present invention as a hydrolytic effect on raw materials from which semi-cellulose is to-A be produced through a high-speed motion with frictional heat. But this' hydrolytic action is 'only possible without anaddition of chemicals iiiandthis is the important factor-when stirring the raw material ahigh speed of 200 to] 1200 and even more turns per minute is applied, thereby producing frictional heat. In this ca'se effects are however produced, which can be attained either with a revolvingor stationary boiling under pressure .without chemicals, nor with a Crusher mill, a finisher, or with a rener unless chemicals are addedv Even in 'this case the eHect of a genuine semi-cellulosaA production does not take place if a stationary or revolving boilingprocess without the addivtion of chemicals and the comblnative effect of beating-engine, linnisher 'and 'reline-one after another has been applied. In'thebest case\a hard, brittle stuff is always produced Without having the qualities of semi-cellulose stuff. On lthe contrary genuine semi-'cellulose is produced from which 20 to 25% of the lignone' and incrusting matter have beenextracted Without the'use of steam and withj 'out adding chemicals if ligneous materials are milled by sharpened knives rotating at a high speed, in a tripleamount of'water, for 2 hours, thereby economizing a boilmg process of 5 hours, a consecutive treatment 1n a beatingengine of 1 hour, in a finisher of 1 hour and a'refine'r of 1 hour or a total of'8 l hours as against-.2 hours in the Leyst process.

This shows therefore that the high speed turns of-the sharpened stirring devices 1n combination with the frictional heat developedhas an up to now' quiteunknown -extrabrdinary effect, but ,also that the high Aeconomically manu speed does not'atithe same time mill the stui so much as to kill it or to produce an inferior product such as mechanical wood pulp. On the contrary, it saves the bres, recovering them'inI their natural length, so that they can, in an increasing measure, be easily and actured vinto full-cellulose, which in the case of white mechanical wood pulp is economically quite impossible. It is only a seaming' contradiction,` that the high turns are opposed by the stationary counter-current arms` d. If' these countercurrent arms were absent, practically the whole mass of stul would turn inside ofthe liner, fand does it better because these engines of the old system work too forcibly and too coarse by, impairing the organic structure of the paper-libres'. The water-cutting,

which results from the rapid water-current,

works so intensively that in connection with the frictionalheat, it dissolves the material more and more and in thi-s stage of the process also parts of resin will be dissolved, and the sharp rotary knives and counter-knives assist and multiply these effects. During the course'of one and the'same stage of manufacdrolytic action water-cutting, and rictional -heat is developed. This process can be assisted by a small percentage/of all oils which contain hydrocarbon.

turing a technical combination between hy,

A very important factor is the increasing rictional heating, of the water, which I now have to consider,1rising to 212 degrees F.

inside oan hour. Asthis frictional heating.

is a steadily rising onethe raw stu has time to fuliyimbibe without any reactive closing up of the cell canals. The stuf'becomes saturated in allits pores up to the center with Water and the increasing heat up to 212 degreesy F. .heightens thev hydrolyte elicot. Schwalbe Judges that (Chemie der Zellulose,

page 20 if boiling Water does not effect a Idissolution of the cellulose, the 7boiling itselfA produces certain changes. Scheurer has discovered (Theis: Die Breitbleiche, page 141) that steaming alone during 60 hours diminishes the tensile strengthof woven matter about 20% land after 360 hours even to 70%. Danish and German inventors even want Ato digest straw stuff without using chemicals, but under pressure and with boiling. IIf however they haveup to the present obtained only a very inferior stuff, which has to be treated too long in the Crusher mill anljv/l1i.`f;li/1

has to pass through the beating-en ine and allthe other auxilia machinery o the old stem, it is scienti` cally generaly known at a boiling process without chemicals prot 5. duces certain changes not only in meat, i'sh,

. fruit, vegetables but especially also in paper pulp, which cannot exclusively be obtained in a cold process. This is the reason Why the action .of frictional heat is much more advantageous than steam boiling, the latter having besides all the other disadvantages already described due to the sudden influx of steam.

`The high speed number of turns generates a hydrodynamical disintegratingv action yand frictional heat. In parallel therewith these effects are heightened by the sharp edges of the revolving and. fixed Vcounter-current knives, in such a manner that by the united action of these novel technical factors semicellulose without' the addition of chemicals f can be manufactured from all cellulose-containing wodand straw-stuffs, including bamboo and bagasse (pressed out sugar cane) palm tree, palm leaves, esparto grass or alfa, lorio,-saboi and all other grasses in one and u the same Universalmachine according to the Leyst system and in one and the same process of manufacture in 2 to 3 hours. If corresponding alkaline matter, acids-or neutral salts are further added to the mass of pulp, the result with. aslightly prolonged time of manufacture will be a highly qualified bleachable cellulose in one and the same Universal-machine of vthe Leyst system, in one and the same process of manufacture. In case these bleachable pulp stu's are to be further bleached this is effected by adding Universal-machine and the same working process in 2 hours. v

The method of working is therefore the following The material is' filled into the Universal-machine including at ythe Sametime three times and in some single instances of raw material sup to fountimes their quantity of Coldwater Without adding any chemicals whatever. AAccording to the stuff, milling sets in with a speed of 200-300-400 up to 1200 turns per minute, during a -period of 2 to 4 hours. After 1 lhours working frictional heating takes place and from 2 hours upwards ready iinished'semi-cellulose may be sorted oii'. If full-'celluloseis to be furnished caustic soda, 5,5 lime or other alkalin matter or neutral salts are added (fromthebeginning) When using acids. th Universal-machine is coveredin the bleaching matter in the same way in the samel interior with an acid-proof material. After 6 to 7 hours work the cellulose is finished andv o can in the same working process, be washed and bleached by adding bleaching materials,

/ then washedl again and' neutralized,

In this manner an entire cellulose manufacturing plant is simplifiedy by this novel 35 boiling;u milling and bleaching procedure prepared and broken up raw containing woods in the Tropics, of the American, African, Asiatic and all other primeval forests, which up till n ow it has not been possible to utilize owing to the enormous costs, can be manufactured into semi-cellulose by means of economical plants, excluding all n cookersfgrounding-engines, beating-engines, reiiners and all import of chemicals, even in the middle of the primeval forests themselves.

' Further all sorts of straw stuffs can be gathered in the farthest countries and utilized as highly qualified rates. j

On the other side now it is possible to transforml such semi-cellulose with great savings of chemicals into finished cellulose. Exact experiments have shown that with 3l/2% caustic soda liquor and a proportion0 of dry stuft' to liquor of 1 to 7.6, six hours boiling of the semi-cellulose has resulted in a finished cellulose capable of making paper having 6075 metre solidity. Since large factories always" se a ratio of waterl to wood (dry weight) of only 3.3 to 1, practically the 31AM@ caustic soda is reduced to 1.52%, from which results a saving of more than 50% in chemicals, regeneration, coal, and labor.

I claim:

1. Process of working up raw cellulosic materials into semi-cellulose, which comprises subjecting the raw material to a com- Lbined hydrodynamicv and frictional heating treatment.

2. Process of working up raw cellulosic materials into semi-cellulose, which comprises mixing the raw material with a greater products at low shipping quantity of water, and subjecting the mixture to the action of high-speed whirling swords and interdigitated stationary swords.

3. Process of working up raw cellulosic materials into semi-cellulose, which com= prises mixing'the raw material with a 2.5 to 7' .6 fold quantity of water, and subjecting the mixture to the action of high-speed .whirling swords and interdigitated stationary swords. l

4. Process of working up raw cellulosic materials into semi-cellulose, which comprises mixing the raw material with a greater quantity of water, and subjecting the mixture to the action of interdigitated stationary and whirling swords, the latter having a rotational speed of at least 150! turns per minute.

5. Process of Working up raw cellulosic materials int'o semi-cellulose, which comprises mixing the raw material with a greater 6 i A l 17,827,716

quantity of water and a small proportion of mineral oil, and subjecting the mixture to the action'of high-speed whirling swords and interdigitated stationary` swords.

6. Process of converting raw cellulosicmaterials into perfect cellulose, which `comprises mixing the raw material with a greater quantity of a chemical liquor, and subjecting thexmixture to the action of high-speed whirl- 10 ing swords andY intel-digitated stationary swords.

,f 7. Process of treating raw cellulosic stul which comprises mixing the stui in a-drum with a greater quantity of water, subjecting 15 the mixture in the drum to the action of higlu- Y 'speed whirling swords and interdi 'tated stationary swords until the stui is ilsintegrated, and then adding a. bleaching agent to the material inthe drum.

zo 8. Process of converting raw cellulosic material into semi-'cellulosa which comprises mixing the raw material with'a greater quanj l tity of water and subjecting the mixture to a combined hydrodynamic and frictional heat- 25 ing process produced bythe action of inter-v digitated high-speed whirling swords and stationary swords. l

9. Process of producing high quality celluv lose from raw cellulosic materials, which comprises mixing the rawy materials with. a greater quantity of water, subjecting the mixture to the disintegrating action of highspeed whirling swords and interdigitated stationary swords until a considerable proportion of the incrusted` substances have been removed, and then addindgva chemical liquor and continuing the' integrating action.

10. Process of producing high quality cellulose from raw lcellulosic materials, which comprises mixing the raw material in a drum with a greater quantity of water, subjecting the mixture in the drum to the disintegrating action of interdigitated high-speed whirling swords and Astationary swords until a considerable proportion of the incrustin sub stances have been removed, then ad ing a chemical liquor and continuing thedisintegrating action until a bleachable .cellulose has been produced, andthen washing and bleaching the cellulose inthe same drum by adding a bleaching agent. j Y .-f

In testimony whereof I ax my `signature.

CARL LEYSpT-KCHENMEISTER. 

